If I Save for Web in Illustrator, there is a very slight color change, which is to be expected. However, when I create a "Save for Web" action and apply it instead of directly using Save for Web, the color is much more vibrant.

I used the exact same settings as when I recorded the action- the only difference is that I'm using an action shortcut so that I don't have to jam my fingers with alt-cmd-shift-s every time. Why is it behaving this way?

If you are saving in PNG format, you can use "pngcheck -v file.png" to look at the contents. In particular, see if there are differences in the color management chunks (iCCP, cHRM, and/or gAMA).
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Glenn Randers-PehrsonMay 22 '14 at 19:57

I was in RGB. I actually solved the issue by restarting Illustrator. Apparently if you change the color profile settings and try to use actions to save, it will use the old settings until you restart. At least that is what I think is going on.
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JustinMay 22 '14 at 23:45